DETERMINATION OF PESTICIDES IN EDIBLE OILS BY GC-MS/MS

Importance of the Topic

The determination of pesticide residues in edible oils addresses a major food safety concern, as oils are lipid-rich matrices prone to carry nonpolar contaminants. Regulatory bodies demand robust, sensitive and reliable methods to detect trace levels of multiple pesticide classes in complex oil samples.

Objectives and Study Overview

This study evaluates a streamlined workflow for the multi-residue analysis of 150 pesticides in olive oil. Two sample preparation strategies are compared: a reference method employing hexane defatting and SPE cleanup, and an alternative method replacing hexane with a freeze-out defatting step coupled with SPE. The performance of both approaches is assessed on recovery, matrix cleanup and instrument sensitivity. A procedural standards calibration is also explored to correct for low recoveries in challenging compounds.

Methods and Instrumentation Used

Samples from retail bottles were spiked with target pesticides prior to extraction. Key steps include:

• Extraction solvent: acetonitrile for broad polarity range.
• Defatting approaches: Method 1 uses hexane; Method 2 uses freezing at low temperature to precipitate lipids.
• Cleanup: Oasis PRiME HLB SPE pass-through cartridge to remove residual fats.
• Internal standard: triphenyl phosphate added before GC injection.
• Detection: GC-EI-MS/MS analysis on Xevo TQ-GC system operated in multiple reaction monitoring mode.

Main Results and Discussion

Replacing hexane defatting with a freeze-out step significantly improved recoveries for organochlorine pesticides (e.g., aldrin recovery increased from 29.6% to 58.7%). Subsequent SPE cleanup yielded recoveries above 70% for all 150 analytes, confirming minimal retention on the HLB cartridge. Procedural standards calibration corrected for low extraction efficiencies, achieving near-quantitative measured recoveries (>100% trueness for hexachlorobenzene and aldrin) and excellent linearity (R2 > 0.998). The method attained a sensitivity down to 0.005 mg/kg for the most challenging compounds.

Benefits and Practical Applications of the Method

The proposed workflow offers several advantages:

• Reduced solvent consumption and faster sample preparation compared to GPC and hexane defatting.
• Robust cleanup of high-fat matrices, minimizing GC liner and column contamination.
• High throughput capability for routine QA/QC laboratories.
• Accurate multi-residue quantitation across diverse pesticide classes.

Future Trends and Potential Applications

Further developments may include:

• Extension to other high-lipid foods such as nuts and avocados.
• Integration of automated QuEChERS-SPE platforms for higher throughput.
• Adoption of high-resolution MS detectors for non-targeted screening.
• Matrix-specific procedural calibration strategies for improved method trueness.

Conclusion

The combination of freeze-out lipid removal, Oasis PRiME HLB SPE cleanup and Xevo TQ-GC MS/MS detection provides a green, sensitive and reliable method for the analysis of 150 pesticide residues in edible oils, meeting stringent regulatory and quality control requirements.

Reference

• European Union (2017), Document No. SANTE 11813/2017. Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticides Residues Analysis in Food and Feed